Generally, it is old to provide a well safety valve for controlling the fluid flow through a well tubing, such as shown in U.S. Pat. No. 3,786,866, in which the valve is adapted to be positioned in the well tubing and a longitudinal movable tubular member controls the movement of the valve closure member. Generally, a tubular member is actuated by hydraulic pressure for moving the valve closure member between a closed and open position.
However, in the past, excessive hydraulic pressure has been applied to the well safety valve, generally during the opening operation, causing damage to some component of the valve such as the tubular member or the valve closure member.
The present invention is directed to an improved subsurface safety valve which is provided with a fail-safe mechanism which is actuated to release upon the application of a predetermined force less than a force sufficient to cause damage to the valve. The mechanism is reactivable and also allows the valve to be used as a lockout for locking the valve closure member in the open position. The valve may also incorporate a permanent lockout section whereby the valve will then provide either a temporary or a permanent lockout mode of operation.